Golf Club
1. Field of the Invention
The present invention relates to a golf club by which the directional stability and flight distance of a shot ball can be improved.
2. Prior Art
In a conventional wooden club, as well as to a metal wood club, a head is in such a shape that, as shown by two dashed line in FIG. 1, it gradually expands from a shaft side to a toe side. The center of gravity of the head is set at a position inclined toward the toe side rather than the center of the projection plane of the head, thereby the head speed of the golf club may be increased at the time of impacting on the ball.
Also in a conventional golf club of an iron type, according to the similar theory, an end of the back side of a club face part is, when seen from a plane, smoothly connected to the hosel, through a neck part, forming a curve (See dashed line A in FIG. 6) and thus the center of gravity of the, club is set at a position slightly inclined toward a toe side.
However, when the center of gravity of the head inclines toward the toe side, as shown by two dashed line in FIG. 2, and when the head B is rotated with holding an end A of the club shaft, a radius R0 of the rotation, with its center line of the rotation positioned at the vertical line made by suspending an upper end of the shaft, increases. Therefore, the metal wood club and the iron club, as shown in FIGS. 3(a) and 11(a), respectively, are apt to cause covering motion (which means the phenomenon that the toe side goes fast than the shaft side as if the toe side rotates around the shaft side) at each head toe side just before impacting.
For the purpose of inhibiting a hook flying of the shot ball, caused by the covering motion, in the metal wood club, as shown by two dashed line in FIG. 1, a head face surface usually has such a shape that the shaft side expands slightly more forward than the toe side. Accordingly, curvature along the transverse direction of the face surface and curvature along longitudinal direction of the face surface are not the same; usually curvature along longitudinal direction is larger than that along the transverse direction.
On the other hand, as shown in FIG. 10, the covering motion is not the only problem in the iron club; that is, the center of gravity of the iron club slightly inclines toward the toe side in the club face part, therefore for advanced golfers whose down swings are faster than those of beginners, a toe down phenomenon, in which the neck part is twisted downwardly by an accelerated motion applied to the head and thus the toe side of the club face part tends to be lowered, resulting in duff shot.
Accordingly, for the purpose of overcoming the defects of the conventional club head, the inventor, as a result of his sharp research, has converted the basic concept of designing the club head to a new one in order to provide a golf club head by which improvement in the directional stability and flight distance of the shot ball can be realized. That is the object of the present invention.
The present invention has been completed on the inventive concept found by us that due to the property of the sling motion of the club head round the gravity center thereof, in which a heavier part goes forward and a lighter part does not catch up with the heavier part in a manner that the heavier part and the lighter part rotate around the gravity center axis, the conventional club head is subjected not only to the above-mentioned covering movement but also to a pull-back phenomenon in the shaft side as a reaction of the covering movement, accordingly resulting in substantial decrease of the speed of the head. The present invention is, therefore, to provide a golf club which head is formed in such a manner that the amount of a shaft side is increased as much as the amount of a head toe side is decreased so as to shift the center of gravity of the head toward the shaft side and a radius of a rotation, with its center line of the rotation positioned at a vertical line made by suspending an upper end of a shaft, is decreased.
Mere shift of the center of gravity of the head toward the shaft side is not enough to overcome the covering motion of the head; at the same time, the weight balance of the head must be maintained. Therefore, it is advantageous to increase the amount of the shaft side in the head as much as that of the toe side decreases so as to maintain the weight balance of the head. Due to this, the center of gravity of the head usually inclines toward the shaft area by the amount having been shifted.
According to the present invention, as shown by solid line in FIG. 2, since the center of gravity of the head inclines toward the shaft side, when the head is rotated by holding the end of the club shaft, the radius SLAYING of the rotation is smaller than the conventional radius R0 of the rotation. Moreover due to the increased amount of the shaft side, with use of the sling motion in which the heavier part tends to go forward and the lighter part tends to be pulled backward just before impact, as shown in FIG. 3(b), it is difficult to cause the covering motion apt to take place in the toe side and the draw phenomenon apt to take place in the shaft side, which results in the improvement in the speed of the head upon giving the impact.
In applying the present invention to a metal wood club, the curvatures along the transverse direction and along the longitudinal direction of the face surface are substantially the same. Since the flight direction of the shot golf ball is dominated by both curvatures along the transverse direction and along the longitudinal direction of the face surface of a point where the impact is given, when the curvatures are not the same, the flight direction is not controlled to a desired direction. In the present invention, however, the covering motion of the head at the time of the impact is inhibited by shifting the center of gravity of the head toward the shaft side, resulting in that the head face surface is formed by a sphere having substantially the same curvatures along both directions of the face surface, which spherical face is most suitable for giving an impact causing the shot ball controlled. Moreover, since it is difficult to cause the covering motion of the head upon giving an impact, the shot ball tends to direct to the extension of the line connecting the center C of spherical body defining the spherical face and the position where the impact was given, by which superior directional stability of the shot ball is ensured.
In applying the present invention to an iron club, it is preferable to form a back side 122 of a club face part 102 by extending the back side 122 until it passes through the center axis (a) of the hosel part 103 (See FIG. 6), and moreover it is preferable to increase thickness A of the back side 122 of a neck part 4 by shifting a part of the weight of the toe side B (See FIG. 8). Due to this, although the design is out of the conventional common knowledge in the light of the conventional toe-heel balance, the center of gravity is located at, or almost at the intersection point of diagonals passing across the club face part, by which good balance is maintained, return of the toe in hitting a ball is suppressed by 70% and the cause for duffing can be solved (See FIG. 11). Therefore secure down strokes can be ensured. Moreover in the light of the design, thickness of a blade can be increased, by which sufficient Spinning shot ball can be made.
Further, since the center of gravity is located at, or almost at the intersection point of diagonals passing across the club face part, different from the conventional iron, a toe down phenomenon apt to take place upon giving an impact can be overcome (See FIG. 10) and the weight distribution suitable for the motion going in and out from a heel is completed, resulting in preventation of mistakes caused by duffing.
In the present invention, when the club face part 2 is designed so as to slightly open by about 1.5xc2x0 against the ball upon addressing, the defect of the conventional club, in which the head easily turns after the impact and therefore golfers are apt to duff (See FIG. 11(a)), can be overcome. Namely, an impact is given in a slightly open position and immediately after this, the position becomes square and then the head turns little by little, which makes the shot ball to fly in a high draw trajectory (See FIG. 11(b)).